Aflatoxin-resistant corn?

Mid-South corn farmers would love to scratch aflatoxin off their list of worries. Research being conducted by Brooks Blanche, LSU agronomist and breeder, could help lead to such list revisions.

“Basically, I’m evaluating the potential to develop corn inbred lines that have resistance to aflatoxin,” says Blanche. “We are approaching this with small steps and, at this point, want to see if there is potential for corn breeding that focuses on Mid-South production issues, including resistance to aflatoxin.”

In years past, Blanche’s predecessor, Steve Moore, had collected and evaluated several exotic tropical lines resistant to aflatoxin. When working with corn, a ‘line’ is half of a hybrid. “Basically, you breed inbred lines and cross the results to produce an F1 hybrid. So, Moore had evaluated some exotic inbred lines he thought had some resistance. That’s kind of where the project was when I took over.”

Blanche will now test some of the inbred lines and additional ones secured from the world collection.

“After we’ve run the tests and have identified those with truly high levels of resistance, if any, we’ll begin a breeding and development program. We’ll try to select for adaptation to the Mid-South growing conditions: hot, sometimes dry environments. And heat and drought are conducive to aflatoxin epidemics.”

Years from now, as inbred lines are developed, “we’ll cross them back to a common tester. That will create hybrid corn seed for multi-location yield trials in Louisiana and throughout the Mid-South.”

The work — funded by the Louisiana Soybean and Grain Research Promotion Board — will be conducted at the Dean Lee Research Station in Alexandria, La., where Blanche is now based. Until last January, he had been working with medium-grain rice breeding at the Crowley station in south Louisiana.

How do the researchers get aflatoxin into their test plots?

“We try to plant on the late side. Since the disease responds to heat and drought, the later we plant the better it is for the tests. Then, we’ll come in with some concentrated inoculum — Aspergillus flavus — and inoculate the ears at mid-silk.”

The inoculum will be applied with a tree-marking gun supplied by a USDA group led by Paul Williams at Mississippi State University. The needle is inserted between the cob and shuck and the inoculum is injected on the developing kernels.

“That way we’re guaranteed there’s inoculum in those ears. Then, right before harvest, we’ll pull the ears (which will be marked with orange spray paint) and run tests to see how much aflatoxin is present in each line, or hybrid.”